Question
      
        The locus of the middle points of chords of the parabola $${y^2} = 8x$$  drawn through the vertex is a parabola whose :      
       A.
        focus is $$\left( {2,\,0} \right)$$              
       B.
        latus rectum $$ = 8$$              
       C.
        focus is $$\left( {0,\,2} \right)$$              
       D.
        latus rectum $$ = 4$$                 
              
            
                Answer :  
        latus rectum $$ = 4$$      
             Solution :
        If the middle point of a chord is $$\left( {\alpha ,\,\beta } \right)$$  then $$\alpha  = \frac{{2{t^2} + 0}}{2},\,\,\beta  = \frac{{4t + 0}}{2}$$
Eliminating $$t,\,\alpha  = {\left( {\frac{\beta }{2}} \right)^2}.$$   So, the locus is $${y^2} = 4x.$$